The invention relates in general to aircraft pilot ejection safety devices and in particular to a safety device for mitigating toe strike during pilot ejection from an aircraft.
Both small and large aircraft pilots place their legs within the narrow foot well (or foot wells) of an aircraft cockpit to reach the rudder pedals. The foot well is generally defined by the instrument panel and the floor of the aircraft. During the ejection process, as the legs are withdrawn upward through the foot wells, it is possible for the feet and toes to strike the top of the foot well and instrument console. This condition is commonly known as “toe strike” and can lead to serious injury.
Although the acceleration forces of ejection do help pull the legs down, the rapid rise of the seat, an occupant's leg size and the confines of the cockpit, particularly the foot well, can work against clearing the feet from the instrument console. The Air Force and Navy have developed a set of anthropometrical cases to describe the range of the aircrew population, see Table 1 below.
TABLE 1Joint DOD Anthropometric Cases (partial listing of attributes)Case 4Case 2Case 3TallMediumMediumSittingBuildBuildHeightCase 5Case 6Case 7Case 8Case 1ShortLongShortOverallLongestOverallLargestFeatureSmallLimbsLimbsLimbsLargeLimbsSmallTorsoButtock-knee21.321.326.522.727.427.920.825.4lengthKnee-height18.719.123.320.624.724.818.123.2sittingThigh18.5-25.017.1-25.020.2-27.617.6-26.318.6-29.219.1-29.717.8-25.218.6-29.1circumferencerangeBoot Size5-13
In Case 6 of Table 1, the geometry of combining a long buttock-knee and tibia (knee-height sitting) results in the knee being farther forward than in any other case. The larger thigh circumference can create a large thigh tangent angle, a space between the ejection seat and the bottom of the thigh that must be made up during the ejection process. As a result, the ejection seat can be in a slightly higher position after it fully supports the thigh. Therefore, the larger tibia is confined, takes longer to clear the same area compared to other cases, thereby resulting in the foot injury.
This type of foot injury may also occur with combinations of Table 1 Features and other human factors not defined in Table 1, in combination with ejection seat height adjustment prior to ejection. Other factors relating to the construction of the aircraft, including but not limited to the cockpit and placement of the ejection seat within the cockpit, can also affect the likelihood of injury.
In such a case an airbag system in accordance with the present invention can mitigate the toe strike damage by 1) receiving its initiation signal from the initiation sequencing system; 2) initiating its gas generator; 3) deploying from its frangible container; 4) deflecting the occupant's limb, particularly the lower leg, and particularly the foot and toes, as the ejection seat (which has also been previously been initiated) rises from the cockpit; and 5) collapsing harmlessly out of the escape path for the remainder of the ejection sequence.
The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings.